dig return values

[Chris Buxton]

On May 22, 2009, at 4:40 PM, Scott Haneda wrote:
> On May 22, 2009, at 3:52 PM, David Forrest wrote:
>>> I have searched for "dig return codes" and also looked at the man  
>>> page, leading me to nothing definitive.
>>>
>>> Does `dig` have return codes that I can use to make some form of  
>>> automated tests?
>>>
>>> 	foo=`dig NS example.com @ns2.example.com +short +time=2 +tries=1`
>>> 	echo $foo
>>>
>>> 	; <<>> DiG 9.4.3-P1 <<>> NS example.com @ns2.example.com +short  
>>> +time=2
>>> 	+tries=1 ;;
>>> 	global options: printcmd ;;
>>> 	connection timed out; no servers could be reached
>>>
>>> I do not know, nor would I want to have to know, all the possible  
>>> return strings I may get back.  My needs are simple, I believe any  
>>> ANSWER of > 0 I would determine to be true, any timeout of any  
>>> form I would determine to be false.
>>>
>>> Can anyone point me to docs on return codes, or is this going to  
>>> amount to string parsing?  If it does, how much deviation on  
>>> return messages are there from the various dig versions that have  
>>> been released?
>>>
>>> Thank you.
>>>
>>
>> my dig (version DiG 9.6.1b1) returns RC 0 on both an answer and a  
>> connection timeout, and would seem to require a string parsing for  
>> a useful branch. F9 64 system.
>
>
> Would you mind sharing with me how you tested that return value?  I  
> am not seeing that bahavior at all, I get a true return for  
> anything.  I have not been able to get false as of yet.

0 is true (success), anything else is false (error). This allows for  
multiple error codes and is standard for Unix commands.

To see the result of a command, use "echo $?" immediately afterward.  
For example:

# foo=`dig`; echo $?
0

# foo=`dig @192.0.2.1`; echo $?
9

# foo=`dig @invalid.name`; echo $?
10

Those results come from dig version 9.4.3-P1. In the second example,  
there is no host at the specified address. In the third example, the  
name given for the server to query is invalid.

Chris Buxton
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